1. Field of the Invention
The invention in general relates to electro-acoustic transducers and more particularly to a simplified method for assembling a transducer of the longitudinal resonator type.
2. Description of the Prior Art
Many transducer units include a plurality of components which must be glued together during the assembly operation. For example a Tonpilz or longitudinal resonator type of transducer includes a head mass for projection and/or receipt of acoustic energy, a tail mass operative as an inertial element and active transducer means interposed between and coupled to the head and tail masses.
The active transducer means is generally comprised of a stack of rings of a ceramic piezoelectric having interposed ring electrodes to which electrical connections are made.
The method of building the transducer assembly is a very time consuming and therefore costly operation. The electrodes and piezoelectric rings are adhesively joined requiring the hand application of the adhesive to each side of the piezoelectric ring after which the stack is placed into a clamping device while the adhesive cures. After curing the stack is removed, necessary wires are soldered to the electrodes and the structure cleaned such as by means of a solvent for removing grease.
The head and tail masses are prepared for adhesive by means of degreasing and sandblasting operation and the cleaned stack, as well as electrically insulating washers on either end of the stack, is interposed between, and coupled to, the head and tail masses and secured in place by means of a stress bolt connecting the head and tail masses. The operation requires the hand application of adhesive to both sides of the insulating washers (or to one side of the washer and the corresponding side of the head or tail mass to which it is abutting). After the second curing the assembly requires another recleaning and sandblasting and since operation might be at elevated voltages an anti-arcing compound is placed over the stack to prevent arc over from an electrode of one polarity to an electrode lead of an opposite polarity. A typical anti-arcing compound which is utilized includes a solid such as acrylic resin in combination with a solvent such as toluene and trichlorethane, representing an irritating and hazardous solution to an assembler.
The assembly of the present invention eliminates the above enumerated costly and objectionable procedures and further lends itself to automatic production techniques.